This disc brake thing.

[oldroadman]

I see the Spanish have now decided to ban discs in competition and sportives. I can understand the worry, their insurers are probably reading all the news about a possible hazard and won't want to be paying claims for alleged disc related injuries. It's money driving the issue, just as money drove the manufacturers to push for road discs. Now I don't have a problem about discs as a principle, but I do think that to allow mixing of braking systems in races is simply daft. When one rider can allegedly stop faster than another simply because of equipment, there is always a potential problem. The only answer is a cut off point when all rim brakes are excluded from road racing, which will mean every single rider will need a new bike! How happy the manufacturers will be!
This is not a pro problem, it's a problem for amateur races, where skill levels can be a bit marginal anyway, especially at the entry/lower levels, as it is. Put a mixed peloton of new and inexperienced and less skilled riders together, add in two braking systems with different potential power, and that's a recipe for carnage. After which the claim/blame rodent lawyers will be all over it. Then racing might be uninsurable, so no racing. Well done the marketeers - who won't care because there will be plenty of riders pretending they are in races (or sportives as we know them) who will have all the bling and will buy all the kit anyway.
Eventually change will come, but it has to be carefully managed, this is a worrying time, glad I'm retired!
Could I just ask all the experts out there, what is this "modulation" that is so improved, is it what we used to call "feel" with those quaint things that grip the rims and stop a bike very efficiently when properly adjusted and used correctly. Which are actually a kind of disc brake, after all it's callipers squeezing a flat surface via pads, just like my car...

 

[Kajjal]

To see one effect check YouTube for disc v rim brakes test done on quality bikes. In the dry on a good road surface with similar riders not much difference. In the wet the disc bike pulled up bike lengths earlier. Imagine for what ever reason on a wet ride in a large tightly packed group the rider near the front with discs brakes very hard. Those on rim brakes would come through the back of them unable to stop fast enough. The same was true on less than perfect road surfaces.

Also they did an 18km downhill with disc brakes on the whole time with no braking issues, just the heat of the disc.

 

[User169]

There's a thread for this already.

@Moderators - please could you merge with the existing thread?

 

[Yellow Saddle]

Modulation is a buzz-word that's easily overused but it does merit some explanation. I would define it as fine and predictable control of the brakes. For brakes to be easily modulatable (I'm patenting that word as we speak) they have to provide stopping force in a perfectly linear fashion. Some brakes, such as those old rubbish Campagnolo Delta brakes and brakes found on modern time trial bikes and older roller cam brakes, don't apply force in a linear fashion. Usually, the lever's travel gives exponential output force at the wheel. Campagnolo Delta brakes for instance, have a mechanical advantage that ranges between 1 and infinity and that in a very short lever travel distance. This has the effect that if you brake hard and harder, you have to really be conscious not to apply much more force. With linear brakes, if you pull the lever X mm, the brakes deliver Y force and if you pull the lever 2Xmm, it delivers 2Y force.
Some Shimano V-brakes from the early 1990s had the option for linear or exponential and this came with a warning that the exponential setting (called M something) was only for experts. Obviously everybody is an expert and the consequences proved that.

Futher, modulation is good when the movement is smooth. Gritty cables don't offer good modulation but delivers increasing and decreasing stopping force in jerky curves. Drum brakes, be it on a car or bicycle, don't modulate well. They have a self-servo action that catches you with surprise lock-up.

A good feel could still provide poor modulation, I'd say.

Just as an aside, note that disc brakes only provide quicker reaction time (for the brakes, not the rider) in wet conditions. Both disc and rim brakes will provide exactly the same stopping force once the rim brake has been wiped dry and had warmed up. Admittedly this requires some distance, but once that hurdle is over, all else is equal. In the dry, the two are exactly the same and can't cause a peloton pile-up.

 

[raleighnut]

Having seen the injuries supposedly inflicted by disc brakes (a bit like being gouged by a blunt serrated edge knife) I think they should be banned until a form of shrouding is fitted to the disc/caliper.

 

[Smokin Joe]

I can only speak as someone who only ever had calipers on a road bike, but now have discs on a recumbent trike. Apples and pears to some extent, but considering the trike weighs at least twice as much as my last road bike the discs bring me to a stop in more or less the same distance (If pushed, I would say less), but in a much more controllable fashion. Rolling downhill at speed the discs are more predictable than rim brakes with less effort to apply and finer control.

Can't say how they feel on a road bike of course, but of those who post here and elsewhere after swapping to discs I haven't come across anyone who wasn't pleased with the change.

Re Raleighnut's post, the key word is "Supposedly". Having read what those involved had to say I have my doubts. Discs on motorcycles are much larger, spin faster and have been in use for over forty years without issue. And they do have multi bike pile ups in all forms of motorcycle racing.

 

[User482]

Having seen the injuries supposedly inflicted by disc brakes (a bit like being gouged by a blunt serrated edge knife) I think they should be banned until a form of shrouding is fitted to the disc/caliper.

Next UCI move?

 

[oldroadman]

I can only speak as someone who only ever had calipers on a road bike, but now have discs on a recumbent trike. Apples and pears to some extent, but considering the trike weighs at least twice as much as my last road bike the discs bring me to a stop in more or less the same distance (If pushed, I would say less), but in a much more controllable fashion. Rolling downhill at speed the discs are more predictable than rim brakes with less effort to apply and finer control.

Can't say how they feel on a road bike of course, but of those who post here and elsewhere after swapping to discs I haven't come across anyone who wasn't pleased with the change.

Re Raleighnut's post, the key word is "Supposedly". Having read what those involved had to say I have my doubts. Discs on motorcycles are much larger, spin faster and have been in use for over forty years without issue. And they do have multi bike pile ups in all forms of motorcycle racing.

Too right. With riders in full leathers and armour, who tend to get thrown clear of the moto in most cases. So no disc damage, but plenty of broken bones and bruises. This is an apples and bananas comparison. That said, I think the REAL danger is mixed systems in the same race. It has to be all rim or all disc. Manufacturers would love it to be all disc because then all the riders would need new bikes....result if you want to sell kit. Trebles all round!

 

[PhilDawson8270]

Motocross have used disc covers for years.

Both to protect others from spinning discs since spectators and stewards can be close, and riders don't wear leather, and to protect the disc and caliper from stones. The methods to sort the "issues" are there, and easy to implement.

The whole thing comes down to UCI simply not wanting to go move on it.

 

[bianchi1]

The main fact is disc brakes on road bikes are ugly. I was confronted by some Giant disk bikes in my lbs the other day and nearly threw up...I stumbled backwards only to catch a glimpse of a zipp wheel with a huge chunky hub and metal plate attached....the horror.

Thankfully my faith in humanity was restored by looking at a colnago fully kitted out with Campagnolo, rim brakes and all.

 

[Yellow Saddle]

The main fact is disc brakes on road bikes are ugly. I was confronted by some Giant disk bikes in my lbs the other day and nearly threw up...I stumbled backwards only to catch a glimpse of a zipp wheel with a huge chunky hub and metal plate attached....the horror.

Thankfully my faith in humanity was restored by looking at a colnago fully kitted out with Campagnolo, rim brakes and all.

This is interesting, this aesthetics thing.

In the good old days we had skinny-tubed bikes with large saddles complete with cheeks down the side. Then came the first fat-tubed bikes (Cannondale) and people said they were ugly. Soon the saddles became more skimpily dressed and lost their cheeks and now people say that is ugly. Then tubes got fatter and fatter and people started to favour those. Frame tubes got fatter, saddles skimpier. Then the retrorevival thing happened, steel tubes were in fashion again and restorations were done. However, in many really good restorations you'll notice modern saddles without cheeks. Those old saddles still appear ugly. Then the organic tube shape fashion started fuelled by carbon mouldings and hydroformed aluminium. That was considered ugly and straight-gauge tubes as beautiful. Now discs are ugly. Soon you'll be used to the new look with their fat forks and think skinny forks are ugly or anorexic. Don't forget the 29er revolution. Suddenly 26" wheels looked odd, even ugly. But just two years ago 29ers looked odd and ugly.

Ugly is in the eye of the beholder, and his/her eye is fickle.

 

[raleighnut]

1937 design for a saddle.

 

[arallsopp]

I can only speak as someone who only ever had calipers on a road bike, but now have discs on a recumbent trike. Apples and pears to some extent, but considering the trike weighs at least twice as much as my last road bike the discs bring me to a stop in more or less the same distance (If pushed, I would say less).

Same here, only on a recumbent bike. When riding with rim caliper uprights, I have to be quite careful about heaving on the anchors, as the bike behind me tends to find me stopping very quickly. I've learned to sit up before I start slowing (airbrake, plus signal to the rider behind) as otherwise the speed I can shed knots becomes quite scary for those that follow. I suspect its more to do with sitting 'behind' the brakes on a 'bent, but I do know that even a beautifully maintained rim brake won't stop in the distance that I can unless they're already on the brakes before I start to squeeze.

 

[Yellow Saddle]

Same here, only on a recumbent bike. When riding with rim caliper uprights, I have to be quite careful about heaving on the anchors, as the bike behind me tends to find me stopping very quickly. I've learned to sit up before I start slowing (airbrake, plus signal to the rider behind) as otherwise the speed I can shed knots becomes quite scary for those that follow. I suspect its more to do with sitting 'behind' the brakes on a 'bent, but I do know that even a beautifully maintained rim brake won't stop in the distance that I can unless they're already on the brakes before I start to squeeze.

It is not the rim brakes on a safety bike (standard bike) that limits its stopping distance but its endover limits. It will do an endo if you stop quick enough. On a recumbent or trike your CoG is much, much lower and you can benefit from the extra stopping force supplied by discs.

If two safety bikes, one with discs and one with calipers were to do a braking competition the minimum stopping distance would be equal.

 

[Wafer]

The main fact is disc brakes on road bikes are ugly

Or, rather than being a fact, it could be a subjective opinion....